Low-k Si-O-C-H composite films were prepared using bis-trimethylsilylmethane as a precursor and oxygen in a rf plasma reactor. The growth rate of the Si-O-C-H composite film followed a second-order exponential decay function. This behavior could be explained by the formation of nanosized voids due to Si-CH3 and OH-related bonds included in the film. OH-related bonds were detected in films deposited at 30 degrees C, but could not be observed for the films deposited above 60 degrees C. In contrast, Si-CH3 bonds were also detected at 30 degrees C, but decreased monotonically up to 210 degrees C and were absent of higher temperatures. After postannealing the film deposited at 30 OC, the Si-CH3 bonds were unchanged, but the OH-related bonds were easily removed. This film showed a low dielectric constant of 2.44 and leakage current density of 4.4 x 10(-7) A/cm(2) at 1 MV/cm.